Scratch resistant glass and method of making

ABSTRACT

Methods of manufacturing a glass-based article includes exposing a glass-based substrate having a lithium aluminosilicate composition to an ion exchange treatment to form the glass-based article. The ion exchange treatment including a molten salt bath having a concentration of a sodium salt in a range from 8 mol % to 100 mol %. The glass-based article includes sodium having a non-zero varying concentration extending from a surface of the glass-based article to a depth of the glass-based article The glass-based article has compressive stress layer extending from the surface to a spike depth of layer from 4 micrometers to 8 micrometers. The glass-based article includes a molar ratio of potassium oxide (K2O) to sodium oxide (Na2O) averaged over a distance from the surface to a depth of 0.4 micrometers that is greater than or equal to 0 and less than or equal to 1.8.

This application is a divisional of and claims the benefit of priorityunder 35 U.S.C § 121 to U.S. application Ser. No. 16/826,473, filed Mar.23, 2020, which claims the benefit of priority under 35 U.S.C. § 119(e)of U.S. Provisional Application Ser. No. 62/826,300, filed on Mar. 29,2019, the content of which is relied upon and incorporated herein byreference in its entirety.

BACKGROUND Field

The present specification generally relates to a scratch-resistantglass. More particularly, the specification relates to a method ofproviding a glass with improved scratch resistance.

Technical Background

Ion exchangeable glasses are widely used as cover glasses and in thebodies of electronic devices. Although ion exchange provides enhancedsurface strength to a glass, including improvement in hardness, theglass is still susceptible to scratches caused by exposure to materialsthat are harder than the glass.

Attempts to improve scratch or abrasion resistance typically includemanipulating a composition of the glass itself to increase hardness, useof alternate materials, or applying hard coatings to the glass surface.For example, lithium-based glasses were developed, which improvedmechanical performance. The Li-based glasses have been shown to havesuperior drop performance, which allows for these glasses to be droppedfrom higher and higher heights before failure (glass breaks/fracture)occurs. In order to improve scratch performance in conjunction withother mechanical performance, boron can be added to open the tightlypacked network of the glass.

It has been a continuous effort for glass makers and handheld devicemanufacturers to improve scratch performance of handheld devices.

Accordingly, a need exists for glasses that can be strengthened, such asby ion exchange, and that have the mechanical properties that allow themto be formed as scratch resistant glass articles.

SUMMARY

Aspects of the disclosure pertain to glass-based articles and methodsfor their manufacture.

In an aspect, the glass-based article comprises a lithiumaluminosilicate composition; sodium having a non-zero varyingconcentration extending from a surface of the glass-based article to adepth of the glass-based article; a spike depth of layer (DOL_(spike))that is greater than or equal to 4 micrometers and less than or equal to8 micrometers; and a molar ratio of potassium oxide (K₂O) to sodiumoxide (Na₂O) averaged over a distance from the surface to a depth of 0.4micrometers that is greater than or equal to 0 and less than or equal to1.8.

In an aspect, the glass-based article comprises: a lithiumaluminosilicate composition; sodium having a non-zero varyingconcentration extending from a surface of the glass-based article to adepth of the glass-based article; a spike depth of layer (DOL_(spike))that is greater than or equal to 4 micrometers and less than or equal to8 micrometers; and an average compressive stress (CS_(avg)) of greaterthan or equal to 115 MPa over a depth from 15 micrometers to 40micrometers.

In an aspect, the glass-based article comprises: sodium having anon-zero varying concentration extending from a surface of theglass-based article to a depth of the glass-based article; an averagecompressive stress (CS_(avg)) of greater than or equal to 150 MPa over adepth from 15 micrometers to 40 micrometers; and a molar ratio ofpotassium oxide (K₂O) to sodium oxide (Na₂O) averaged over a distancefrom the surface to a depth of 0.4 micrometers that is greater than orequal to 0 and less than or equal to 1.8.

In an aspect, a method of manufacturing a glass-based article comprises:exposing a glass-based substrate having opposing first and secondsurfaces defining a substrate thickness (t) and having a lithiumaluminosilicate composition to an ion exchange treatment comprising amolten salt bath having a concentration of a sodium salt in the range ofgreater than or equal to 8 mol % to less than or equal to 100 mol %; andforming the glass-based article having: sodium having a non-zero varyingconcentration extending from a surface of the glass-based article to adepth of the glass-based article; a compressive layer extending from thesurface to a spike depth of layer (DOL_(spike)) that is greater than orequal to 4 micrometers and less than or equal to 8 micrometers; and amolar ratio of potassium oxide (K₂O) to sodium oxide (Na₂O) averagedover a distance from the surface to a depth of 0.4 micrometers that isgreater than or equal to 0 and less than or equal to 1.8.

Additional features and advantages will be set forth in the detaileddescription which follows, and in part will be readily apparent to thoseskilled in the art from that description or recognized by practicing theembodiments described herein, including the detailed description whichfollows, the claims, as well as the appended drawings.

It is to be understood that both the foregoing general description andthe following detailed description describe various embodiments and areintended to provide an overview or framework for understanding thenature and character of the claimed subject matter. The accompanyingdrawings are included to provide a further understanding of the variousembodiments, and are incorporated into and constitute a part of thisspecification. The drawings illustrate the various embodiments describedherein, and together with the description serve to explain theprinciples and operations of the claimed subject matter.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying figures, which are incorporated in and constitute apart of this specification, illustrate several embodiments describedbelow.

FIG. 1 schematically depicts a cross-section of a glass havingcompressive stress layers on surfaces thereof according to embodimentsdisclosed and described herein;

FIG. 2 is a schematic representation of a stress profile including aknee stress;

FIG. 3A is a plan view of an exemplary electronic device incorporatingany of the glass articles disclosed herein;

FIG. 3B is a perspective view of the exemplary electronic device of FIG.3A;

FIG. 4 is a graph of oxide molar concentration as a function of depth inthe glass article from a first surface (0 micrometers) for anembodiment;

FIG. 5 is a graph of oxide molar concentration as a function of depth inthe glass article from a first surface (0 micrometers) for a comparativeexample;

FIG. 6 is a graph of oxide molar concentration as a function of depth inthe glass article from a first surface (0 micrometers) for a comparativeexample;

FIG. 7 is a graph of oxide molar concentration as a function of depth inthe glass article from a first surface (0 micrometers) for anembodiment;

FIG. 8 is a graph of oxide molar concentration as a function of depth inthe glass article from a first surface (0 micrometers) for anembodiment;

FIG. 9 is a graph of stress (MPa) versus position (micrometers) from asurface for embodiments of a glass-based article and a comparativeexample;

FIG. 10 is a graph of stress (MPa) versus position (micrometers) from asurface for embodiments of a glass-based article;

FIG. 11 is a graph of oxide molar concentration as a function of depthin the glass article from a first surface (0 micrometers) for anembodiment;

FIG. 12 is a graph of stress (MPa) versus position (micrometers) from asurface for embodiments of a glass-based article;

FIG. 13 is a graph of oxide molar concentration as a function of depthin the glass article from a first surface (0 micrometers) for acomparative example;

FIG. 14 is a graph of stress (MPa) versus position (micrometers) from asurface for comparative glass-based articles;

FIG. 15 is a graph of stress (MPa) versus position (micrometers) from asurface for embodiments of a glass-based article and a comparativeexample; and

FIG. 16 is a graph of stress (MPa) versus position (micrometers) from asurface for embodiments of a glass-based article and comparativeexamples.

DETAILED DESCRIPTION

Before describing several exemplary embodiments, it is to be understoodthat the disclosure is not limited to the details of construction orprocess steps set forth in the following disclosure. The disclosureprovided herein is capable of other embodiments and of being practicedor being carried out in various ways.

Reference throughout this specification to “one embodiment,” “certainembodiments,” “various embodiments,” “one or more embodiments” or “anembodiment” means that a particular feature, structure, material, orcharacteristic described in connection with the embodiment is includedin at least one embodiment of the disclosure. Thus, the appearances ofthe phrases such as “in one or more embodiments,” “in certainembodiments,” “in various embodiments,” “in one embodiment” or “in anembodiment” in various places throughout this specification are notnecessarily referring to the same embodiment, or to only one embodiment.Furthermore, the particular features, structures, materials, orcharacteristics may be combined in any suitable manner in one or moreembodiments.

Definitions and Measurement Techniques

The terms “glass-based article” and “glass-based substrates” are used toinclude any object made wholly or partly of glass. Laminated glass-basedarticles include laminates of glass and non-glass materials, laminatesof glass and crystalline materials. Glass-based substrates according toone or more embodiments can be selected from soda-lime silicate glass,alkali-alumino silicate glass, alkali-containing borosilicate glass, andalkali-containing aluminoborosilicate glass.

A “base composition” is a chemical make-up of a substrate prior to anyion exchange (IOX) treatment. That is, the base composition is undopedby any ions from IOX. A composition at the center of a glass-basedarticle that has been IOX treated is typically the same as the basecomposition when IOX treatment conditions are such that ions suppliedfor IOX do not diffuse into the center of the substrate. In one or moreembodiments, a central composition at the center of the glass articlecomprises the base composition.

It is noted that the terms “substantially” and “about” may be utilizedherein to represent the inherent degree of uncertainty that may beattributed to any quantitative comparison, value, measurement, or otherrepresentation. These terms are also utilized herein to represent thedegree by which a quantitative representation may vary from a statedreference without resulting in a change in the basic function of thesubject matter at issue. Thus, for example, a glass-based article thatis “substantially free of MgO” is one in which MgO is not actively addedor batched into the glass-based article, but may be present in verysmall amounts as a contaminant. As used herein, the term “about” meansthat amounts, sizes, formulations, parameters, and other quantities andcharacteristics are not and need not be exact, but may be approximateand/or larger or smaller, as desired, reflecting tolerances, conversionfactors, rounding off, measurement error and the like, and other factorsknown to those of skill in the art. When the term “about” is used indescribing a value or an end-point of a range, the disclosure should beunderstood to include the specific value or end-point referred to.Whether or not a numerical value or end-point of a range in thespecification recites “about,” the numerical value or end-point of arange is intended to include two embodiments: one modified by “about,”and one not modified by “about.” It will be further understood that theendpoints of each of the ranges are significant both in relation to theother endpoint, and independently of the other endpoint.

Unless otherwise specified, all compositions described herein areexpressed in terms of mole percent (mol %) on an oxide basis.

A “stress profile” is stress as a function of thickness across aglass-based article. A compressive stress region extends from a firstsurface to a depth of compression (DOC) of the article, and is a regionwhere the article is under compressive stress. A central tension regionextends from the DOC to include the region where the article is undertensile stress.

As used herein, depth of compression (DOC) refers to the depth at whichthe stress within the glass-based article changes from compressive totensile stress. At the DOC, the stress crosses from a positive(compressive) stress to a negative (tensile) stress and thus exhibits astress value of zero. According to the convention normally used inmechanical arts, compression is expressed as a negative (<0) stress andtension is expressed as a positive (>0) stress. Throughout thisdescription, however, positive values of stress are compressive stress(CS), which are expressed as a positive or absolute value—i.e., asrecited herein, CS=|CS|. Additionally, negative values of stress aretensile stress. But when used with the term “tensile”, stress or centraltension (CT) may be expressed as a positive value, i.e., CT=|CT|.Central tension (CT) refers to tensile stress in a central region or acentral tension region of the glass-based article. Maximum centraltension (maximum CT or CT_(max)) may occur in the central tension regionnominally at 0.5•t, where t is the article thickness, which allows forvariation from exact center of the location of the maximum tensilestress. Peak tension (PT) refers to maximum tension measured, which mayor may not be at the center of the article.

A “knee” of a stress profile is a depth of an article where the slope ofthe stress profile transitions from steep to gradual. The knee may referto a transition area over a span of depths where the slope is changing.The knee stress CS_(k) is defined as the value of compressive stressthat the deeper portion of the CS profile extrapolates to at the depthof spike (DOL_(sp)). The DOL_(sp) is reported as measured by asurface-stress meter by known methods. A schematic representation of astress profile including a knee stress is provided in FIG. 2 .

A non-zero metal oxide concentration that varies from the first surfaceto a depth of layer (DOL) with respect to the metal oxide or that variesalong at least a substantial portion of the article thickness (t)indicates that a stress has been generated in the article as a result ofion exchange. The variation in metal oxide concentration may be referredto herein as a metal oxide concentration gradient. The metal oxide thatis non-zero in concentration and varies from the first surface to a DOLor along a portion of the thickness may be described as generating astress in the glass-based article. The concentration gradient orvariation of metal oxides is created by chemically strengthening aglass-based substrate in which a plurality of first metal ions in theglass-based substrate is exchanged with a plurality of second metalions.

As used herein, the terms “depth of exchange”, “depth of layer” (DOL),“chemical depth of layer”, and “depth of chemical layer” may be usedinterchangeably, describing in general the depth at which ion exchangefacilitated by an ion exchange process (IOX) takes place for aparticular ion. DOL refers to the depth within a glass-based article(i.e., the distance from a surface of the glass-based article to itsinterior region) at which an ion of a metal oxide or alkali metal oxide(e.g., the metal ion or alkali metal ion) diffuses into the glass-basedarticle where the concentration of the ion reaches a minimum value, asdetermined by Glow Discharge—Optical Emission Spectroscopy (GD-OES)). Insome embodiments, the DOL is given as the depth of exchange of theslowest-diffusing or largest ion introduced by an ion exchange (IOX)process. DOL with respect to potassium (DOL_(K)) is the depth at whichthe potassium content of the glass article reaches the potassium contentof the underlying substrate. DOL with respect to sodium (DOL_(Na)) isthe depth at which the sodium content of the glass article reaches thesodium content of the underlying substrate.

Unless otherwise specified, CT and CS are expressed herein inmegaPascals (MPa), thickness is express in millimeters and DOC and DOLare expressed in microns (micrometers).

Compressive stress (including surface/peak CS, CS_(max)) and DOL_(sp)are measured by surface stress meter (FSM) using commercially availableinstruments such as the FSM-6000, manufactured by Orihara IndustrialCo., Ltd. (Japan). Surface stress measurements rely upon the accuratemeasurement of the stress optical coefficient (SOC), which is related tothe birefringence of the glass. SOC in turn is measured according toProcedure C (Glass Disc Method) described in ASTM standard C770-16,entitled “Standard Test Method for Measurement of Glass Stress-OpticalCoefficient,” the contents of which are incorporated herein by referencein their entirety.

The maximum central tension (CT) or peak tension (PT) and stressretention values are measured using a scattered light polariscope(SCALP) technique known in the art. The Refracted near-field (RNF)method or SCALP may be used to measure the stress profile and the depthof compression (DOC). When the RNF method is utilized to measure thestress profile, the maximum CT value provided by SCALP is utilized inthe RNF method. In particular, the stress profile measured by RNF isforce balanced and calibrated to the maximum CT value provided by aSCALP measurement. The RNF method is described in U.S. Pat. No.8,854,623, entitled “Systems and methods for measuring a profilecharacteristic of a glass sample”, which is incorporated herein byreference in its entirety. In particular, the RNF method includesplacing the glass article adjacent to a reference block, generating apolarization-switched light beam that is switched between orthogonalpolarizations at a rate of from 1 Hz to 50 Hz, measuring an amount ofpower in the polarization-switched light beam and generating apolarization-switched reference signal, wherein the measured amounts ofpower in each of the orthogonal polarizations are within 50% of eachother. The method further includes transmitting thepolarization-switched light beam through the glass sample and referenceblock for different depths into the glass sample, then relaying thetransmitted polarization-switched light beam to a signal photodetectorusing a relay optical system, with the signal photodetector generating apolarization-switched detector signal. The method also includes dividingthe detector signal by the reference signal to form a normalizeddetector signal and determining the profile characteristic of the glasssample from the normalized detector signal.

General Overview of Properties of Glass-Based Articles

Glass-based articles herein have stress profiles that are designed tohave improved scratch resistance. Unique stress profiles include adesired potassium-sodium molar ratio at or near a surface of theglass-based article and/or a desired compressive stress at a knee and/ora desired average compressive stress over a certain depth of thearticle.

During ion exchange, glasses having base compositions where Na₂O mole %is less than Li₂O mole % can experience significant potassium to lithiumion exchange. Although lithium readily ion exchanges for sodium at veryfast diffusion rates based on their respective ionic radii sizes, whichenables achieving parabolic stress profiles within several hours forlithium glasses, lithium's ion exchange with potassium is much slowerdue to the ionic radius of potassium being significantly larger than Na.Scratch performance of lithium-based glass compositions with Na₂O mole %<<Li₂O mole % can be improved by using high sodium salt (e.g., NaNO₃)concentrations in ion exchange to reduce the amount of potassium tolithium ion exchange. Upon exposure to a treatment bath comprising 100%NaNO₃ salt, scratch performance is significantly improved compared totreatment baths containing less than or equal to 10% NaNO₃ salt. Also,by using LiNO₃ in a treatment bath in combination with greater than orequal to 10% NaNO₃ salt, scratch performance is improved while stillstaying outside of the realm of frangibility. The loads at which lateralcracking appears increase with increasing sodium concentration in thetreatment bath. This also relates to the surface of the glass having asimilar ratio of mol % concentration of potassium to sodium (or even ahigher sodium concentration at the surface).

The methods described herein are advantageous in that by using thespecific bath conditions (high sodium concentration), the resultingstress profile results in a glass with improved scratch performance aswell as good drop performance. This process allow for increased scratchresistance achieved through a stress profile as opposed to compositionchanges seen with boron addition. Ultimately, a user may increase ordecrease scratch performance of a glass through an ion exchange profile.

Reference will now be made in detail to lithium aluminosilicate glassesand scratch resistance according to various embodiments. Alkalialuminosilicate glasses have good ion exchangeability, and chemicalstrengthening processes have been used to achieve high strength and hightoughness properties in alkali aluminosilicate glasses. Sodiumaluminosilicate glasses are highly ion exchangeable glasses with highglass formability and quality. Lithium aluminosilicate glasses arehighly ion exchangeable glasses with high glass quality. Thesubstitution of Al₂O₃ into the silicate glass network increases theinterdiffusivity of monovalent cations during ion exchange. By chemicalstrengthening in a molten salt bath (e.g., KNO₃ or NaNO₃), glasses withhigh strength, high toughness, and high indentation cracking resistancecan be achieved. The stress profiles achieved through chemicalstrengthening may have a variety of shapes that increase the dropperformance, strength, toughness, and other attributes of the glassarticles as well as improved scratch resistance.

Therefore, lithium aluminosilicate glasses with good physicalproperties, chemical durability, and ion exchangeability have drawnattention for use as cover glass. Through different ion exchangeprocesses, greater central tension (CT), depth of compression (DOC), andhigh compressive stress (CS) can be achieved. The stress profilesdescribed herein provide increased fracture resistance for lithiumcontaining glass articles.

In embodiments of glass compositions described herein, the concentrationof constituent components (e.g., SiO₂, Al₂O₃, Li₂O, and the like) aregiven in mole percent (mol %) on an oxide basis, unless otherwisespecified. It should be understood that any of the variously recitedranges of one component may be individually combined with any of thevariously recited ranges for any other component.

Disclosed herein are ion exchange methods and stress profiles forlithium aluminosilicate glass compositions. The stress profiles exhibitscratch resistance. With reference to FIG. 1 , the glass has a thicknesst and a first region under compressive stress (e.g., first and secondcompressive stress layers 120, 122 in FIG. 1 ) extending from thesurface to a depth of compression (DOC) of the glass and a second region(e.g., central region 130 in FIG. 1 ) under a tensile stress or centraltension (CT) extending from the DOC into the central or interior regionof the glass.

The compressive stress (CS) has a maximum or peak value, which typicallyoccurs at the surface of the glass (but such need not be the case as thepeak may occur at a depth from the surface of the glass), and the CSvaries with distance d from the surface according to a function.Referring again to FIG. 1 , the first compressive stress layer 120extends from first surface 110 to a depth d₁ and a second compressivestress layer 122 extends from second surface 112 to a depth d₂.Together, these segments define a compression or CS of glass 100.

The compressive stress of both major surfaces (110, 112 in FIG. 1 ) isbalanced by stored tension in the central region (130) of the glass.

In the glass-based articles, there is an alkali metal oxide having anon-zero concentration that varies from one or both of first and secondsurfaces to a depth of layer (DOL) with respect to the metal oxide. Astress profile is generated due to the non-zero concentration of themetal oxide(s) that varies from the first surface. The non-zeroconcentration may vary along a portion of the article thickness. In someembodiments, the concentration of the alkali metal oxide is non-zero andvaries, both along a thickness range from about 0•t to about 0.3•t. Insome embodiments, the concentration of the alkali metal oxide isnon-zero and varies along a thickness range from about 0•t to about0.35•t, from about 0•t to about 0.4•t, from about 0•t to about 0.45•t,from about 0•t to about 0.48•t, or from about 0•t to about 0.50•t. Thevariation in concentration may be continuous along the above-referencedthickness ranges. Variation in concentration may include a change inmetal oxide concentration of about 0.2 mol % or more along a thicknesssegment of about 100 micrometers. The change in metal oxideconcentration may be about 0.3 mol % or more, about 0.4 mol % or more,or about 0.5 mol % or more along a thickness segment of about 100micrometers. This change may be measured by known methods in the artincluding microprobe.

In some embodiments, the variation in concentration may be continuousalong thickness segments in the range from about 10 micrometers to about30 micrometers. In some embodiments, the concentration of the alkalimetal oxide decreases from the first surface to a value between thefirst surface and the second surface and increases from the value to thesecond surface.

The concentration of alkali metal oxide may include more than one metaloxide (e.g., a combination of Na₂O and K₂O). In some embodiments, wheretwo metal oxides are utilized and where the radius of the ions differfrom one or another, the concentration of ions having a larger radius isgreater than the concentration of ions having a smaller radius atshallow depths, while at deeper depths, the concentration of ions havinga smaller radius is greater than the concentration of ions having largerradius.

In one or more embodiments, the alkali metal oxide concentrationgradient extends through a substantial portion of the thickness t of thearticle. In some embodiments, the concentration of the metal oxide maybe about 0.5 mol % or greater (e.g., about 1 mol % or greater) along theentire thickness of the first and/or second section, and is greatest ata first surface and/or a second surface 0•t and decreases substantiallyconstantly to a value between the first and second surfaces. At thatvalue, the concentration of the metal oxide is the least along theentire thickness t; however the concentration is also non-zero at thatpoint. In other words, the non-zero concentration of that particularmetal oxide extends along a substantial portion of the thickness t (asdescribed herein) or the entire thickness t. The total concentration ofthe particular metal oxide in the glass-based article may be in therange from about 1 mol % to about 20 mol %.

The concentration of the alkali metal oxide may be determined from abaseline amount of the metal oxide in the glass-based substrate ionexchanged to form the glass-based article.

In one or more embodiments, the glass-based article comprises: a molarratio of potassium oxide (K₂O) to sodium oxide (Na₂O) averaged over adistance from the surface to a depth of 0.4 micrometers that is greaterthan or equal to 0 and less than or equal to 1.8, or greater than orequal to 0.2, greater than or equal to 0.4, greater than or equal to0.6; greater than or equal to 0.8, greater than or equal to 1, greaterthan or equal to 1.2, greater than or equal to 1.4, greater than orequal to 1.6; and/or less than or equal to 1.7; less than or equal to1.5; less than or equal to 1.3; less than or equal to 1.1; less than orequal to 0.9; and all values and subranges therebetween. These K₂O toNa₂O molar ratios contribute, at least in part, to the improved scratchresistance of the glass-based articles described herein.

In one or more embodiments, the glass-based article comprises: a spikedepth of layer (DOL_(spike)) that is greater than or equal to 4micrometers, greater than or equal to 4.5 micrometers, greater than orequal to 5 micrometers, greater than or equal to 5.5 micrometers,greater than or equal to 6 micrometers, greater than or equal to 6.5micrometers, greater than or equal to 7 micrometers; and/or less than orequal to 8 micrometers, less than or equal to 7.5 micrometers, less thanor equal to 7 micrometers, including all values and subrangestherebetween.

In one or more embodiments, the glass-based article comprises: apotassium depth of layer (DOL_(K)) that is greater than or equal to 4micrometers, greater than or equal to 4.5 micrometers, greater than orequal to 5 micrometers, greater than or equal to 5.5 micrometers,greater than or equal to 6 micrometers, greater than or equal to 6.5micrometers, greater than or equal to 7 micrometers; and/or less than orequal to 8 micrometers, less than or equal to 7.5 micrometers, less thanor equal to 7 micrometers, including all values and subrangestherebetween.

In one or more embodiments, the glass-based article comprises: sodium anon-zero varying concentration extending from a surface of theglass-based article to a depth (DOL_(Na)) that is greater than or equalto 4 micrometers, greater than or equal to 4.5 micrometers, greater thanor equal to 5 micrometers, greater than or equal to 5.5 micrometers,greater than or equal to 6 micrometers, greater than or equal to 6.5micrometers, greater than or equal to 7 micrometers; and/or less than orequal to 8 micrometers, less than or equal to 7.5 micrometers, less thanor equal to 7 micrometers, including all values and subrangestherebetween.

In one or more embodiments, the glass-based article comprises: anaverage compressive stress (CS_(avg)) over a depth from 15 micrometersto 40 micrometers of greater than or equal to 115 MPa, greater than orequal to 120 MPa, greater than or equal to 125 MPa, greater than orequal to 130 MPa, greater than or equal to 135 MPa, greater than orequal to 140 MPa, greater than or equal to 145 MPa, greater than orequal to 150 MPa, greater than or equal to 155 MPa, greater than orequal to 160 MPa, greater than or equal to 165 MPa, greater than orequal to 170 MPa, including all values and subranges therebetween.

In one or more embodiments, the glass-based article comprises: acompressive stress at a knee (CS_(k)) that is greater than or equal to115 MPa, greater than or equal to 120 MPa, greater than or equal to 125MPa, greater than or equal to 130 MPa, greater than or equal to 135 MPa,greater than or equal to 140 MPa, greater than or equal to 145 MPa,greater than or equal to 150 MPa, greater than or equal to 155 MPa,greater than or equal to 160 MPa, greater than or equal to 165 MPa,greater than or equal to 170 MPa, including all values and subrangestherebetween.

In one or more embodiments, the glass-based article comprises: acompressive stress at a knee (CS_(k)) that is greater than or equal to115 MPa, greater than or equal to 120 MPa, greater than or equal to 125MPa, greater than or equal to 130 MPa, greater than or equal to 135 MPa,greater than or equal to 140 MPa, greater than or equal to 145 MPa,greater than or equal to 150 MPa, greater than or equal to 155 MPa,greater than or equal to 160 MPa, greater than or equal to 165 MPa,greater than or equal to 170 MPa, including all values and subrangestherebetween.

In one or more embodiments, the glass-based article comprises: a depthof compression (DOC) that is greater than or equal to 0.19t, greaterthan or equal to 0.20t, greater than or equal to 0.21t, greater than orequal to 0.22t, greater than or equal to 0.23t, greater than or equal to0.24t, greater than or equal to 0.25t, and/or less than or equal to0.30t, less than or equal to 0.29t, less than or equal to 0.28t, lessthan or equal to 0.27t, less than or equal to 0.26t, less than or equalto 0.25t, less than or equal to 0.24t, less than or equal to 0.23t,including all values and subranges therebetween.

In one or more embodiments, the glass-based article comprises: a depthof compression (DOC) that is greater than or equal to 150 micrometers,greater than or equal to 155 micrometers, greater than or equal to 160micrometers, greater than or equal to 165 micrometers, greater than orequal to 170 micrometers, including all values and subrangestherebetween.

In one or more embodiments, the glass-based article comprises: t in therange of 0.5 mm to 0.8 mm, and all values and subranges therebetween;and/or t may be 0.8 mm or less, 0.75 mm or less, 0.73 mm or less, 0.70mm or less, 0.65 mm or less, 0.6 mm or less, 0.55 mm or less, 0.4 mm orless, 0.3 mm or less, or 0.2 mm or less and/or greater than or equal to0.1 mm, including all values and subranges therebetween.

In one or more embodiments, the glass-based article comprises: a maximumcompressive stress (CS_(max)) that is greater than or equal to 500 MPa,greater than or equal to 550 MPa, greater than or equal to 600 MPa,greater than or equal to 650 MPa, greater than or equal to 700 MPa,greater than or equal to 750 MPa, greater than or equal to 800 MPa,greater than or equal to 850 MPa, greater than or equal to 900 MPa,greater than or equal to 950 MPa, greater than or equal to 1000 MPa,greater than or equal to 1050 MPa, greater than or equal to 1100 MPa,greater than or equal to 1150 MPa, or greater than or equal to 1200 MPa,including all values and subranges therebetween.

In one or more embodiments, the glass-based article comprises: aLi₂O/Na₂O molar ratio that is greater than or equal to 0.10 and lessthan or equal to 0.63, including all values and subranges therebetween.

In combination with the molar ratio of potassium oxide (K₂O) to sodiumoxide (Na₂O) averaged over a distance from the surface to a depth of 0.4micrometers that is greater than or equal to 0 and less than or equal to1.8, the glass-based articles may possess one or a combination of thefollowing features: a lithium aluminosilicate composition; sodium havinga non-zero varying concentration extending from a surface of theglass-based article to a depth of the glass-based article; a spike depthof layer (DOL_(spike)) that is greater than or equal to 4 micrometers,greater than or equal to 4.5 micrometers, greater than or equal to 5micrometers, greater than or equal to 5.5 micrometers, greater than orequal to 6 micrometers, greater than or equal to 6.5 micrometers,greater than or equal to 7 micrometers; and/or less than or equal to 8micrometers, less than or equal to 7.5 micrometers, less than or equalto 7 micrometers, including all values and subranges therebetween; anaverage compressive stress (CS_(avg)) over a depth from 15 micrometersto 40 micrometers of greater than or equal to 115 MPa, greater than orequal to 120 MPa, greater than or equal to 125 MPa, greater than orequal to 130 MPa, greater than or equal to 135 MPa, greater than orequal to 140 MPa, greater than or equal to 145 MPa, greater than orequal to 150 MPa, greater than or equal to 155 MPa, greater than orequal to 160 MPa, greater than or equal to 165 MPa, greater than orequal to 170 MPa, including all values and subranges therebetween; acompressive stress at a knee (CS_(k)) that is greater than or equal to115 MPa, greater than or equal to 120 MPa, greater than or equal to 125MPa, greater than or equal to 130 MPa, greater than or equal to 135 MPa,greater than or equal to 140 MPa, greater than or equal to 145 MPa,greater than or equal to 150 MPa, greater than or equal to 155 MPa,greater than or equal to 160 MPa, greater than or equal to 165 MPa,greater than or equal to 170 MPa, including all values and subrangestherebetween; a depth of compression (DOC) that is greater than or equalto 0.19t, greater than or equal to 0.20t, greater than or equal to0.21t, greater than or equal to 0.22t, greater than or equal to 0.23t,greater than or equal to 0.24t, greater than or equal to 0.25t, and/orless than or equal to 0.30t, less than or equal to 0.29t, less than orequal to 0.28t, less than or equal to 0.27t, less than or equal to0.26t, less than or equal to 0.25t, less than or equal to 0.24t, lessthan or equal to 0.23t, including all values and subranges therebetween,and/or that is greater than or equal to 150 micrometers, greater than orequal to 155 micrometers, greater than or equal to 160 micrometers,greater than or equal to 165 micrometers, greater than or equal to 170micrometers, including all values and subranges therebetween; t in therange of 0.5 mm to 0.8 mm, and all values and subranges therebetween;and/or t may be 0.8 mm or less, 0.75 mm or less, 0.73 mm or less, 0.70mm or less, 0.65 mm or less, 0.6 mm or less, 0.55 mm or less, 0.4 mm orless, 0.3 mm or less, or 0.2 mm or less and/or greater than or equal to0.1 mm; a maximum compressive stress (CS_(max)) that is greater than orequal to 500 MPa, greater than or equal to 550 MPa, greater than orequal to 600 MPa, greater than or equal to 650 MPa, greater than orequal to 700 MPa, greater than or equal to 750 MPa, greater than orequal to 800 MPa, greater than or equal to 850 MPa, greater than orequal to 900 MPa, greater than or equal to 950 MPa, greater than orequal to 1000 MPa, greater than or equal to 1050 MPa, greater than orequal to 1100 MPa, greater than or equal to 1150 MPa, or greater than orequal to 1200 MPa, including all values and subranges therebetween; aLi₂O/Na₂O molar ratio that is greater than or equal to 0.10 and lessthan or equal to 0.63, including all values and subranges therebetween;and at the center of the glass-based article, a base compositioncomprises: 9.39-25 mol % alumina (Al₂O₃), 0.1-20 mol % sodium oxide(Na₂O), and up to 9.01 mol % boron oxide (B₂O₃), and at least onealkaline earth metal oxide, wherein 15 mol %≤(R₂O+R′O—Al₂O₃—ZrO₂)—B₂O₃≤2 mol %, where R is Na and optionally one or more of Li, K, Rb, and Cs,and R′ is one or more of Mg, Ca, Sr, and Ba.

In combination with a spike depth of layer (DOL_(spike)) that is greaterthan or equal to 4 micrometers, greater than or equal to 4.5micrometers, greater than or equal to 5 micrometers, greater than orequal to 5.5 micrometers, greater than or equal to 6 micrometers,greater than or equal to 6.5 micrometers, greater than or equal to 7micrometers; and/or less than or equal to 8 micrometers, less than orequal to 7.5 micrometers, less than or equal to 7 micrometers, includingall values and subranges therebetween, the glass-based articles maypossess one or a combination of the following features: a lithiumaluminosilicate composition; sodium having a non-zero varyingconcentration extending from a surface of the glass-based article to adepth of the glass-based article; molar ratio of potassium oxide (K₂O)to sodium oxide (Na₂O) averaged over a distance from the surface to adepth of 0.4 micrometers that is greater than or equal to 0 and lessthan or equal to 1.8; an average compressive stress (CS_(avg)) over adepth from 15 micrometers to 40 micrometers of greater than or equal to115 MPa, greater than or equal to 120 MPa, greater than or equal to 125MPa, greater than or equal to 130 MPa, greater than or equal to 135 MPa,greater than or equal to 140 MPa, greater than or equal to 145 MPa,greater than or equal to 150 MPa, greater than or equal to 155 MPa,greater than or equal to 160 MPa, greater than or equal to 165 MPa,greater than or equal to 170 MPa, including all values and subrangestherebetween; a compressive stress at a knee (CS_(k)) that is greaterthan or equal to 115 MPa, greater than or equal to 120 MPa, greater thanor equal to 125 MPa, greater than or equal to 130 MPa, greater than orequal to 135 MPa, greater than or equal to 140 MPa, greater than orequal to 145 MPa, greater than or equal to 150 MPa, greater than orequal to 155 MPa, greater than or equal to 160 MPa, greater than orequal to 165 MPa, greater than or equal to 170 MPa, including all valuesand subranges therebetween; a depth of compression (DOC) that is greaterthan or equal to 0.19t, greater than or equal to 0.20t, greater than orequal to 0.21t, greater than or equal to 0.22t, greater than or equal to0.23t, greater than or equal to 0.24t, greater than or equal to 0.25t,and/or less than or equal to 0.30t, less than or equal to 0.29t, lessthan or equal to 0.28t, less than or equal to 0.27t, less than or equalto 0.26t, less than or equal to 0.25t, less than or equal to 0.24t, lessthan or equal to 0.23t, including all values and subranges therebetween,and/or that is greater than or equal to 150 micrometers, greater than orequal to 155 micrometers, greater than or equal to 160 micrometers,greater than or equal to 165 micrometers, greater than or equal to 170micrometers, including all values and subranges therebetween; t in therange of 0.5 mm to 0.8 mm, and all values and subranges therebetween;and/or t may be 0.8 mm or less, 0.75 mm or less, 0.73 mm or less, 0.70mm or less, 0.65 mm or less, 0.6 mm or less, 0.55 mm or less, 0.4 mm orless, 0.3 mm or less, or 0.2 mm or less and/or greater than or equal to0.1 mm; a maximum compressive stress (CS_(max)) that is greater than orequal to 500 MPa, greater than or equal to 550 MPa, greater than orequal to 600 MPa, greater than or equal to 650 MPa, greater than orequal to 700 MPa, greater than or equal to 750 MPa, greater than orequal to 800 MPa, greater than or equal to 850 MPa, greater than orequal to 900 MPa, greater than or equal to 950 MPa, greater than orequal to 1000 MPa, greater than or equal to 1050 MPa, greater than orequal to 1100 MPa, greater than or equal to 1150 MPa, or greater than orequal to 1200 MPa, including all values and subranges therebetween; aLi₂O/Na₂O molar ratio that is greater than or equal to 0.10 and lessthan or equal to 0.63, including all values and subranges therebetween;and at the center of the glass-based article, a base compositioncomprises: 9.39-25 mol % alumina (Al₂O₃), 0.1-20 mol % sodium oxide(Na₂O), and up to 9.01 mol % boron oxide (B₂O₃), and at least onealkaline earth metal oxide, wherein 15 mol %≤(R₂O+R′O—Al₂O₃—ZrO₂)—B₂O₃≤2 mol %, where R is Na and optionally one or more of Li, K, Rb, and Cs,and R′ is one or more of Mg, Ca, Sr, and Ba.

In combination with an average compressive stress (CS_(avg)) over adepth from 15 micrometers to 40 micrometers of greater than or equal to115 MPa, greater than or equal to 120 MPa, greater than or equal to 125MPa, greater than or equal to 130 MPa, greater than or equal to 135 MPa,greater than or equal to 140 MPa, greater than or equal to 145 MPa,greater than or equal to 150 MPa, greater than or equal to 155 MPa,greater than or equal to 160 MPa, greater than or equal to 165 MPa,greater than or equal to 170 MPa, including all values and subrangestherebetween, the glass-based articles may possess one or a combinationof the following features: a lithium aluminosilicate composition; sodiumhaving a non-zero varying concentration extending from a surface of theglass-based article to a depth of the glass-based article; molar ratioof potassium oxide (K₂O) to sodium oxide (Na₂O) averaged over a distancefrom the surface to a depth of 0.4 micrometers that is greater than orequal to 0 and less than or equal to 1.8; a spike depth of layer(DOL_(spike)) that is greater than or equal to 4 micrometers, greaterthan or equal to 4.5 micrometers, greater than or equal to 5micrometers, greater than or equal to 5.5 micrometers, greater than orequal to 6 micrometers, greater than or equal to 6.5 micrometers,greater than or equal to 7 micrometers; and/or less than or equal to 8micrometers, less than or equal to 7.5 micrometers, less than or equalto 7 micrometers, including all values and subranges therebetween; acompressive stress at a knee (CS_(k)) that is greater than or equal to115 MPa, greater than or equal to 120 MPa, greater than or equal to 125MPa, greater than or equal to 130 MPa, greater than or equal to 135 MPa,greater than or equal to 140 MPa, greater than or equal to 145 MPa,greater than or equal to 150 MPa, greater than or equal to 155 MPa,greater than or equal to 160 MPa, greater than or equal to 165 MPa,greater than or equal to 170 MPa, including all values and subrangestherebetween; a depth of compression (DOC) that is greater than or equalto 0.19t, greater than or equal to 0.20t, greater than or equal to0.21t, greater than or equal to 0.22t, greater than or equal to 0.23t,greater than or equal to 0.24t, greater than or equal to 0.25t, and/orless than or equal to 0.30t, less than or equal to 0.29t, less than orequal to 0.28t, less than or equal to 0.27t, less than or equal to0.26t, less than or equal to 0.25t, less than or equal to 0.24t, lessthan or equal to 0.23t, including all values and subranges therebetween,and/or that is greater than or equal to 150 micrometers, greater than orequal to 155 micrometers, greater than or equal to 160 micrometers,greater than or equal to 165 micrometers, greater than or equal to 170micrometers, including all values and subranges therebetween; t in therange of 0.5 mm to 0.8 mm, and all values and subranges therebetween;and/or t may be 0.8 mm or less, 0.75 mm or less, 0.73 mm or less, 0.70mm or less, 0.65 mm or less, 0.6 mm or less, 0.55 mm or less, 0.4 mm orless, 0.3 mm or less, or 0.2 mm or less and/or greater than or equal to0.1 mm; a maximum compressive stress (CS_(max)) that is greater than orequal to 500 MPa, greater than or equal to 550 MPa, greater than orequal to 600 MPa, greater than or equal to 650 MPa, greater than orequal to 700 MPa, greater than or equal to 750 MPa, greater than orequal to 800 MPa, greater than or equal to 850 MPa, greater than orequal to 900 MPa, greater than or equal to 950 MPa, greater than orequal to 1000 MPa, greater than or equal to 1050 MPa, greater than orequal to 1100 MPa, greater than or equal to 1150 MPa, or greater than orequal to 1200 MPa, including all values and subranges therebetween; aLi₂O/Na₂O molar ratio that is greater than or equal to 0.10 and lessthan or equal to 0.63, including all values and subranges therebetween;and at the center of the glass-based article, a base compositioncomprises: 9.39-25 mol % alumina (Al₂O₃), 0.1-20 mol % sodium oxide(Na₂O), and up to 9.01 mol % boron oxide (B₂O₃), and at least onealkaline earth metal oxide, wherein 15 mol %≤(R₂O+R′O—Al₂O₃—ZrO₂)—B₂O₃≤2 mol %, where R is Na and optionally one or more of Li, K, Rb, and Cs,and R′ is one or more of Mg, Ca, Sr, and Ba.

In an aspect, the glass-based article comprises a lithiumaluminosilicate composition; sodium having a non-zero varyingconcentration extending from a surface of the glass-based article to adepth of the glass-based article; a spike depth of layer (DOL_(spike))that is greater than or equal to 4 micrometers and less than or equal to8 micrometers; and a molar ratio of potassium oxide (K₂O) to sodiumoxide (Na₂O) averaged over a distance from the surface to a depth of 0.4micrometers that is greater than or equal to 0 and less than or equal to1.8.

In an aspect, the glass-based article comprises: a lithiumaluminosilicate composition; sodium having a non-zero varyingconcentration extending from a surface of the glass-based article to adepth of the glass-based article; a spike depth of layer (DOL_(spike))that is greater than or equal to 4 micrometers and less than or equal to8 micrometers; and an average compressive stress (CS_(avg)) of greaterthan or equal to 115 MPa over a depth from 15 micrometers to 40micrometers.

In an aspect, the glass-based article comprises: sodium having anon-zero varying concentration extending from a surface of theglass-based article to a depth of the glass-based article; an averagecompressive stress (CS_(avg)) of greater than or equal to 150 MPa over adepth from 15 micrometers to 40 micrometers; and a molar ratio ofpotassium oxide (K₂O) to sodium oxide (Na₂O) averaged over a distancefrom the surface to a depth of 0.4 micrometers that is greater than orequal to 0 and less than or equal to 1.8.

Glass-Based Substrates

Examples of glasses that may be used as substrates may includealkali-alumino silicate glass compositions or alkali-containingaluminoborosilicate glass compositions, though other glass compositionsare contemplated. Specific examples of glass-based substrates that maybe used include but are not limited to an alkali-alumino silicate glass,an alkali-containing borosilicate glass, an alkali-alumino borosilicateglass, an alkali-containing lithium alumino silicate glass, or analkali-containing phosphate glass. The glass-based substrates have basecompositions that may be characterized as ion exchangeable. As usedherein, “ion exchangeable” means that a substrate comprising thecomposition is capable of exchanging cations located at or near thesurface of the substrate with cations of the same valence that areeither larger or smaller in size.

In one or more embodiments, glass-based substrates may include alithium-containing aluminosilicate.

In embodiments, the glass-based substrates may be formed from anycomposition capable of forming the stress profiles. In some embodiments,the glass-based substrates may be formed from the glass compositionsdescribed in U.S. application Ser. No. 16/202,691 titled “Glasses withLow Excess Modifier Content,” filed Nov. 28, 2018, the entirety of whichis incorporated herein by reference. In some embodiments, the glassarticles may be formed from the glass compositions described in U.S.Application No. 16/202,767 titled “Ion-Exchangeable Mixed AlkaliAluminosilicate Glasses,” filed Nov. 28, 2018, the entirety of which isincorporated herein by reference.

The glass-based substrates may be characterized by the manner in whichit may be formed. For instance, the glass-based substrates may becharacterized as float-formable (i.e., formed by a float process),down-drawable and, in particular, fusion-formable or slot-drawable(i.e., formed by a down draw process such as a fusion draw process or aslot draw process). In embodiments, the glass-based substrates may beroll formed.

Some embodiments of the glass-based substrates described herein may beformed by a down-draw process. Down-draw processes produce glass-basedsubstrates having a uniform thickness that possess relatively pristinesurfaces. Because the average flexural strength of the glass article iscontrolled by the amount and size of surface flaws, a pristine surfacethat has had minimal contact has a higher initial strength. In addition,down drawn glass articles have a very flat, smooth surface that can beused in its final application without costly grinding and polishing.

Some embodiments of the glass-based substrates may be described asfusion-formable (i.e., formable using a fusion draw process). The fusionprocess uses a drawing tank that has a channel for accepting moltenglass raw material. The channel has weirs that are open at the top alongthe length of the channel on both sides of the channel. When the channelfills with molten material, the molten glass overflows the weirs. Due togravity, the molten glass flows down the outside surfaces of the drawingtank as two flowing glass films. These outside surfaces of the drawingtank extend down and inwardly so that they join at an edge below thedrawing tank. The two flowing glass films join at this edge to fuse andform a single flowing glass article. The fusion draw method offers theadvantage that, because the two glass films flowing over the channelfuse together, neither of the outside surfaces of the resulting glassarticle comes in contact with any part of the apparatus. Thus, thesurface properties of the fusion drawn glass article are not affected bysuch contact.

Some embodiments of the glass-based substrates described herein may beformed by a slot draw process. The slot draw process is distinct fromthe fusion draw method. In slot draw processes, the molten raw materialglass is provided to a drawing tank. The bottom of the drawing tank hasan open slot with a nozzle that extends the length of the slot. Themolten glass flows through the slot/nozzle and is drawn downward as acontinuous glass article and into an annealing region.

In an embodiment, a base composition comprises: 9.39-25 mol % alumina(Al₂O₃), 0.1-20 mol % sodium oxide (Na₂O), and up to 9.01 mol % boronoxide (B₂O₃), and at least one alkaline earth metal oxide, wherein 15mol %≤(R₂O+R′O—Al₂O₃—ZrO₂)—B₂O₃ ≤2 mol %, where R is Na and optionallyone or more of Li, K, Rb, and Cs, and R′ is one or more of Mg, Ca, Sr,and Ba.

In one or more embodiments, the glass-based substrates described hereinmay exhibit an amorphous microstructure and may be substantially free ofcrystals or crystallites. In other words, the glass-base substratesarticles exclude glass-ceramic materials in some embodiments.

Ion Exchange (IOX) Treatment

Chemical strengthening of glass substrates having base compositions isdone by placing the ion-exchangeable glass substrates in a molten bathcontaining cations (e.g., K+, Na+, Ag+, etc) that diffuse into the glasswhile the smaller alkali ions (e.g., Na+, Li+) of the glass diffuse outinto the molten bath. The replacement of the smaller cations by largerones creates compressive stresses near the top surface of glass. Tensilestresses are generated in the interior of the glass to balance thenear-surface compressive stresses.

With respect to ion exchange processes, they may independently be athermal-diffusion process or an electro-diffusion process. Non-limitingexamples of ion exchange processes in which glass is immersed inmultiple ion exchange baths, with washing and/or annealing steps betweenimmersions, are described in U.S. Pat. No. 8,561,429, by Douglas C.Allan et al., issued on Oct. 22, 2013, entitled “Glass with CompressiveSurface for Consumer Applications,” and claiming priority from U.S.Provisional Patent Application No. 61/079,995, filed Jul. 11, 2008, inwhich glass is strengthened by immersion in multiple, successive, ionexchange treatments in salt baths of different concentrations; and U.S.Pat. No. 8,312,739, by Christopher M. Lee et al., issued on Nov. 20,2012, and entitled “Dual Stage Ion Exchange for Chemical Strengtheningof Glass,” and claiming priority from U.S. Provisional PatentApplication No. 61/084,398, filed Jul. 29, 2008, in which glass isstrengthened by ion exchange in a first bath is diluted with an effluention, followed by immersion in a second bath having a smallerconcentration of the effluent ion than the first bath. The contents ofU.S. Pat. Nos. 8,561,429 and 8,312,739 are incorporated herein byreference in their entireties.

After an ion exchange process is performed, it should be understood thata composition at the surface of a glass article may be different thanthe composition of the as-formed glass article (i.e., the glass articlebefore it undergoes an ion exchange process). This results from one typeof alkali metal ion in the as-formed glass, such as, for example Li⁺ orNa⁺, being replaced with larger alkali metal ions, such as, for exampleNa⁺ or K⁺, respectively. However, the glass composition at or near thecenter of the depth of the glass article will, in embodiments, stillhave the composition of the as-formed glass article.

In an aspect, a method of manufacturing a glass-based article comprises:exposing a glass-based substrate having opposing first and secondsurfaces defining a substrate thickness (t) and having a lithiumaluminosilicate composition to an ion exchange treatment comprising amolten salt bath having a concentration of a sodium salt in the range ofgreater than or equal to 8 mol % to less than or equal to 100 mol %; andforming the glass-based article having: sodium having a non-zero varyingconcentration extending from a surface of the glass-based article to adepth of the glass-based article; a compressive layer extending from thesurface to a spike depth of layer (DOL_(spike)) that is greater than orequal to 4 micrometers and less than or equal to 8 micrometers; and amolar ratio of potassium oxide (K₂O) to sodium oxide (Na₂O) averagedover a distance from the surface to a depth of 0.4 micrometers that isgreater than or equal to 0 and less than or equal to 1.8.

The glass-based article made by the methods herein may comprise one ormore of the following: an average compressive stress (CSavg) of greaterthan or equal to 115 MPa over a depth from 15 micrometers to 40micrometers; and a depth of compression (DOC) that is greater than orequal to 0.19t and/or greater than or equal to 150 micrometers. A basecomposition of the glass-based substrate comprises a molar ratio ofsodium oxide (Na₂O) to lithium oxide (Li₂O) of less than or equal to0.63. The sodium salt may comprise: NaNO₃, Na₂CO₃, Na₃PO₄, Na₂SO₄,Na₃BO₃, NaCl, or combinations thereof.

In an embodiment, the method is conducted using a single ion exchangetreatment, wherein the molten salt bath comprises the sodium salt in anamount of greater than or equal to 8 weight % and less than or equal to100 weight %, a lithium salt in an amount of greater than or equal to 0weight % and less than or equal to 10 weight %, and a potassium salt inan amount of greater than or equal to 0 weight % and less than or equalto 90 weight %. The sodium salt may comprise sodium nitrate (NaNO₃), thelithium salt comprises lithium nitrate (LiNO₃), and the potassium saltcomprises potassium nitrate (KNO₃).

In an embodiment, the method is conducted using a dual ion exchangetreatment, wherein a first molten salt bath comprises the sodium salt inan amount of greater than or equal to 8 weight % and less than or equalto 100 weight %, a lithium salt in an amount of greater than or equal to0 weight % and less than or equal to 10 weight %, and a potassium saltin an amount of greater than or equal to 0 weight % and less than orequal to 90 weight %; and a second molten salt bath comprises the sodiumsalt in an amount of greater than or equal to 8 weight % and less thanor equal to 100 weight %, a lithium salt in an amount of greater than orequal to 0 weight % and less than or equal to 10 weight %, and apotassium salt in an amount of greater than or equal to 0 weight % andless than or equal to 90 weight %. In each molten salt bath, the sodiumsalt may comprise sodium nitrate (NaNO₃), the lithium salt compriseslithium nitrate (LiNO₃), and the potassium salt comprises potassiumnitrate (KNO₃).

The methods therein may be effective to form the glass-based substratehaving a molar ratio of potassium oxide (K₂O) to sodium oxide (Na₂O)averaged over a distance from the surface to a depth of 0.4 micrometersthat is greater than or equal to 0 and less than or equal to 1.8.

The methods herein may be effective to form the glass-based substratehaving a spike depth of layer (DOL_(spike)) that is greater than orequal to 4 micrometers and less than or equal to 8 micrometers.

End Products

The glass-based articles disclosed herein may be incorporated intoanother article such as an article with a display (or display articles)(e.g., consumer electronics, including mobile phones, tablets,computers, navigation systems, and the like), architectural articles,transportation articles (e.g., automobiles, trains, aircraft, sea craft,etc.), appliance articles, or any article that requires sometransparency, scratch-resistance, abrasion resistance or a combinationthereof. An exemplary article incorporating any of the glass articlesdisclosed herein is shown in FIGS. 3A and 3B. Specifically, FIGS. 3A and3B show a consumer electronic device 300 including a housing 302 havingfront 304, back 306, and side surfaces 308; electrical components (notshown) that are at least partially inside or entirely within the housingand including at least a controller, a memory, and a display 310 at oradjacent to the front surface of the housing; and a cover 312 at or overthe front surface of the housing such that it is over the display. Insome embodiments, the cover 312 and/or housing 302 may include any ofthe glass articles disclosed herein.

EXAMPLES

Various embodiments will be further clarified by the following examples.In the Examples, prior to being strengthened, the Examples are referredto as “substrates”. After being subjected to strengthening, the Examplesare referred to as “articles” or “glass-based articles”.

Glass substrates according to Compositions A-C were ion exchanged andthe resulting articles tested.

Compositions A and B had the following compositions. Composition A:17.83 mol % Al₂O₃, 6.11 mol % B₂O₃, 4.41 mol % MgO, 1.73 mol % Na₂O,58.39 mol % SiO₂, 0.08 mol % SnO₂, 0.18 mol % K₂O, 0.02 mol % Fe₂O₃,0.58 mol % CaO, and 10.66 mol % Li₂O (0.00 mol % SrO, 0.00 mol % ZnO,and 0.00 mol % P₂O₅); and a Na₂O/Li₂O molar ratio of 0.16. CompositionB: 12.88 mol % Al₂O₃, 1.84 mol % B₂O₃, 2.86 mol % MgO, 2.39 mol % Na₂O,70.96 mol % SiO₂, 0.07 mol % SnO₂, 0.02 mol % Fe₂O₃, 8.13 mol % Li₂O,and 0.85 mol % ZnO, (0.00 mol % K₂O, 0.00 mol % CaO, 0.00 mol % SrO, and0.00 mol % P₂O₅); and a Na₂O/Li₂O molar ratio of 0.29.

Composition C had the following composition. Composition C: 15.17 mol %Al₂O₃, 6.73 mol % B₂O₃, 1.02 mol % MgO, 4.32 mol % Na₂O, 63.27 mol %SiO₂, 0.03 mol % SnO₂, 0.02 mol % Fe₂O₃, 1.55 mol % CaO, 6.86 mol %Li₂O, and 1.03 mol % SrO, (0.00 mol % K₂O, and 0.00 mol % P₂O₅, 0.00 mol% ZnO); and a Na₂O/Li₂O molar ratio of 0.63.

Several glass articles were prepared under varying ion exchangeconditions, including 0 mol % sodium salt to 100 mol % sodium salt.Scratch testing of the glass articles of the examples was completedusing a Bruker UMT (universal mechanical tester) with a Knoop geometrydiamond tip from Gilmore Diamonds. The tip was loaded into a surface ofthe glass article at a rate of 0.14 N/s to a desired load of 5N or 8N,with two to five scratches per load, at which point the tip was draggedlaterally through the article at a rate of 9.34 mm/min. From there, thediamond tip was unloaded at a rate of 0.14 N/s.

Examples 1-6 and Examples A-D (Comparative)—Glass Articles based onComposition A—SIOX

Glass articles were formed based on substrates according to CompositionA, which were ion exchanged according to the bath conditions describedin Table 1A.

TABLE 1A Step1 Step 1 NaNO₃/KNO₃/LiNO₃ Step 1 time Example t (mm) (mol%) (° C.) (hours) A 0.8 0/100/0 450 7 Comparative B 0.8 6/94/0 450 8.4Comparative C 0.8 7/93/0 450 8 Comparative D 0.8 7/93/0 450 12Comparative 1 0.8 11.8/86.2/2 450 8.4 2 0.8 100/0/0 450 1 3 0.89.8/88.2/2 450 8.4 4 0.75 10/88.8/1.2 450 8.4 5 0.75 12/86.2/1.8 450 8.46 0.8 30/70/0 450 8

Table 1B provides the scratch data.

TABLE 1B Depth of Compression Example 5N 8N (DOC) A Lateral crackingArticle fractured — Comparative present B Lateral cracking Lateralcracking 175 micrometers Comparative present present (21.9% ofthickness) C — — — Comparative D Lateral cracking Lateral cracking —Comparative present present 1 NO cracking Some Lateral 176 micrometerscracking present (22.0% of thickness) 2 NO cracking NO cracking — 3 NOcracking NO cracking 169 micrometers (21.1% of thickness) 4 NO crackingNO cracking — 5 — — — 6 NO cracking Some lateral — cracking

Example A (comparative) of Table 1B shows that at 5N, lateral crackingappeared on the glass article when no sodium was present in the ionexchange bath. Increasing the load to 8N resulted in fracturing of thearticle. As sodium concentration of the ion exchange bath increased, thethreshold at which lateral cracking formed was increased. While ExampleB (comparative) having a bath of 6%Na/94%K showed lateral cracking at5N, the article did not break when loaded to 8N. Example 1 having acondition of 12%Na further increased the threshold—no lateral crackingwas observed at 5N—however some lateral cracking, fewer instancesrelative to Example B, occurred at 8N. For Example 6, where the bathconcentration was increased to 30% Na, no lateral cracking was observedat 5N—however some lateral cracking occurred at 8N. For Example 2, wherethe bath concentration was increased to 100% Na, no lateral cracking wasobserved at 5N or 8N. The articles of Examples 2 and 6 were, however,frangible. At a nominal 10%NaNO₃ concentration similar behavior between0.75 mm (Example 4) and 0.8 mm (Example 3) thickness is observed.

FIGS. 4-8 provide GDOES elemental profiles of oxide molar concentrationas a function of depth in the glass article from a first surface (0micrometers) for Examples 1, C, D, 4, and 6, respectively.

For Example 1 of FIG. 4 , the averages under the curve of measuredconcentration values over the distance from 0 micrometers to 0.4micrometers were: 4.1 for Na₂O mol %and 4.82 for K₂O mol %. Theresulting molar ratio of potassium oxide (K₂O) to sodium oxide (Na₂O)was 1.16. The depth of layer of potassium (DOL_(K)) was 4.7 micrometers.

For Example C (comparative) of FIG. 5 , the averages under the curve ofmeasured concentration values over the distance from 0 micrometers to0.4 micrometers were: 4.2 for Na₂O mol % and 8.4 for K₂O mol %. Theresulting molar ratio of potassium oxide (K₂O) to sodium oxide (Na₂O)was 2.0. The depth of layer of potassium (DOL_(K)) was 7.2 micrometers.

For Example D (comparative) of FIG. 6 , the averages under the curve ofmeasured concentration values over the distance from 0 micrometers to0.4 micrometers were: 3.7 Na₂O mol % and 8.1 for K₂O mol %. Theresulting molar ratio of potassium oxide (K₂O) to sodium oxide (Na₂O)was 2.21. The depth of layer of potassium (DOL_(K)) was 7.9 micrometers.

For Example 4 of FIG. 7 , taking the average under the curve of measuredconcentration values over the distance from 0 micrometers to 0.4micrometers, the average Na₂O mol % was 4.64 and the average K₂O mol %was 4.88. The resulting molar ratio of potassium oxide (K₂O) to sodiumoxide (Na₂O) was 1.05. The depth of layer of potassium (DOL_(K)) was 5.0micrometers.

For Example 6 of FIG. 8 , taking the average under the curve of measuredconcentration values over the distance from 0 micrometers to 0.4micrometers, the average Na₂O mol % was 8.78 and the average K₂O mol %was 3.31. The resulting molar ratio of potassium oxide (K₂O) to sodiumoxide (Na₂O) was 0.38. The depth of layer of potassium (DOL_(K)) was 6.2micrometers.

The scratch resistance of Example 1, where the average K₂O to Na₂O molarratio over the distance from 0 micrometers to 0.4 micrometers was 1.25was better than that of Examples C and D, where the ratio was 2.0 and2.27 respectively. Both Examples 4 and 6, with ratios of 1.05 and 0.38,respectively, displayed excellent scratch resistance.

From this, it is generally concluded that stress profiles advantageousfor scratch resistance have a Na₂O mol % at or near the surface that issimilar to or within a couple of mol % relative to the K₂O mol %.Moreover, preferred average K₂O to Na₂O molar ratio over the distancefrom 0 micrometers to 0.4 micrometers are greater than or equal to 0 toless than or equal to 1.8, including all values and ranges therebetween.

FIG. 9 is a graph of stress (MPa) versus position (micrometers) from asurface for Examples 1, 3, and B all of the same thickness. Althoughsimilar compressive stresses at depths between 10-30 micrometers depthare shown for the two inventive and one comparative articles, Example 1,having higher Na mol % in the salt bath has a significantly increasedload for onset of lateral cracking as compared to Example B as noted inTable 1B.

For Examples 1 and 3, both shown FIG. 9 , average compressive stressesover the depth of 15 micrometers to 40 micrometers based on the averagearea under the curve in FIG. 9 were both 140 MPa. Example 1 had a depthof layer (DOL_(spike)) of 5.1 micrometers and a CS_(knee) of 138 MPa.Example 3 had a depth of layer (DOL_(spike)) of 5.3 micrometers and aCS_(knee) of 141 MPa.

FIG. 10 is a graph of stress (MPa) versus position (micrometers) from asurface for Examples 4-5. Example 4, which used 10%NaNO₃/1.2%LiNO₃,resulted in a stress profile having about 40 MPa higher surface CS,which can be beneficial for overstress failures.

Examples 7-8 and Example E (Comparative)—Glass Articles based onComposition B—SIOX

Glass articles were formed based on substrates according to CompositionB, which were ion exchanged according to the bath conditions describedin Table 2A.

TABLE 2A Step1 t NaNO₃/KNO₃/LiNO₃ Step 1 Step 1 time Example (mm) (mol%) (° C.) (hours) E 0.8 6.5/93.5/0 430 4.5 Comparative 7 0.8 12/86/2 4304.5 8 0.8 100/0/0 430 0.75

Table 2B provides the scratch data.

TABLE 2B Depth of Compression Example 5N 8N (DOC) E Lateral crackingLateral cracking — Comparative present present 7 NO cracking Lateralcracking 180 micrometers present (22.5% of thickness) 8 NO cracking NOcracking —

Example E (comparative) of Table 2B shows that at both 5N and 8N,lateral cracking appeared on the glass article when there was low sodiumpresent in the ion exchange bath. As sodium concentration of the ionexchange bath increased, the threshold at which lateral cracking formedwas increased. Example 7 having a condition of 12%Na further increasedthe threshold—no lateral cracking was observed at 5N—however there waslateral cracking at 8N. Example 8, where the bath concentration wasincreased to 100% Na, no lateral cracking was observed at 5N or 8N.

For Example 7 of FIG. 11 , taking the average under the curve ofmeasured concentration values over the distance from 0 micrometers to0.4 micrometers, the average Na₂O mol % was 3.55 and the average K₂O mol% was 4.47. The resulting molar ratio of potassium oxide (K₂O) to sodiumoxide (Na₂O) was 1.26. The depth of layer of potassium (DOL_(K)) was 6.1micrometers.

FIG. 12 is a graph of stress (MPa) versus position (micrometers) from asurface for Examples 7 and E. CS_(knee) for Example 7 (116 MPa) improvedby ˜16 MPa relative to the CS_(knee) for Comparative Example E (˜100MPa).

For Example 7, shown in FIG. 12 , an average compressive stress over thedepth of 15 micrometers to 40 micrometers based on the average areaunder the curve in FIG. 12 was 102 MPa. Example 7 had a depth of layer(DOL_(spike)) of 6.5 micrometers and a CS_(knee) of 116 MPa.

Example F (Comparative)—Glass Article Based on Composition C—DIOX

Glass articles were formed based on substrates according to CompositionC, which were ion exchanged according to the bath conditions describedin Table 3A.

TABLE 3A Step 1 Step 1 Step 2 Step 2 t NaNO₃/KNO₃/LiNO₃ Step 1 timeNaNO₃/KNO₃/LiNO₃ Step 2 time Example (mm) (mol %) (° C.) (hours) (mol %)(° C.) (hours) F 0.8 15/85/0 430 6 4/96/0 430 1.25 Comparative

Table 3B provides the scratch data.

TABLE 3B Depth of Compression Example 5N 8N (DOC) F NO cracking NOcracking 176.5 micrometers Comparative (22.1% of thickness)

FIG. 13 provides a GDOES elemental profile of oxide molar concentrationas a function of depth in the glass article from a first surface (0micrometers) for Example F (comparative). Taking the average under thecurve of measured concentration values over the distance from 0micrometers to 0.4 micrometers, the average Na₂O mol % was 3.15 and theaverage K₂O mol % was 7.5. The resulting molar ratio of potassium oxide(K₂O) to sodium oxide (Na₂O) was 2.37.

FIG. 14 is a graph of stress (MPa) versus position (micrometers) from asurface for Examples E and F. In the center of the glass, Example E(comparative) had a Na₂O/Li₂O mole ratio of 0.29, whereas Example F(comparative) had a Na₂O/Li₂O mole ratio of 0.63. The two glasscompositions had comparable stress profiles.

Example F (comparative) of Table 3B shows that at both 5N and 8N, therewas no lateral cracking upon DIOX treatment. In Example E (comparative)of Table 2B, at both 5N and 8N, lateral cracking appeared on the glassarticle when there was low sodium present in the ion exchange bath.Scratch performance was improved (no lateral cracking observed at 8N)for the similar stress profiles (FIG. 14 ) when the glass compositionhad a 0.63 Na₂O/Li₂O mole ratio in the center of the glass (Example F)vs 0.29 (Example E). At 0.63 Na₂O/Li₂O mole ratio, IOX of the K+ in thesalt with Li in the glass is low, and K+ is ion exchanging with Na inglass, while Na+ in the salt is ion exchanging with Li in the glass.Thus the glass molar volume in the surface layer was not significantlydecreased by ion exchanging a large K ion for the small Na ion andembrittling the surface.

For Example F (comparative), shown in FIG. 14 , an average compressivestress over the depth of 15 micrometers to 40 micrometers based on theaverage area under the curve in FIG. 14 was 92 MPa. Example F had adepth of layer (DOL_(spike)) of 8.1 micrometers and a CS_(knee) of 109MPa.

Examples 9-10—Glass Articles Based on Composition A—DIOX

Glass articles were formed based on substrates according to CompositionA, which were ion exchanged according to the bath conditions describedin Table 4A.

TABLE 4A Step 1 Step 1 Step 2 Step 2 t NaNO₃/KNO₃/LiNO₃ Step 1 timeNaNO₃/KNO₃/LiNO₃ Step 2 time Example (mm) (mol %) (° C.) (hours) (mol %)(° C.) (hours)  9 0.8 15.0/81.0/4.0 + 450 8 15.0/85.0/0 450 0.5 0.5%Silicic Acid 10 0.8 11.5/84.7/3. 450 13 15.0/85.0/0 450 0.5

Table 4B provides the scratch data.

TABLE 4B Depth of Compression Example 5N 8N (DOC) 9 NO cracking Lateralcracking present 157 micrometers Sample 1 Large cracking^(A) 2 of 5scratches (19.6% of thickness) Max. Width: 585.4 μm and 632.6 μm 9 NOcracking Lateral cracking present — Sample 2 Large cracking^(A) 2 of 5scratches Max. Width: 513.2 μm and 484.4 μm 10 NO cracking Lateralcracking present 170.5 micrometers Sample 1 Large cracking^(A) 1 of 5scratches (21.3% of thickness) Max. Width: 467.3 μm 10 NO crackingLateral cracking present — Sample 2 Large cracking^(A) 4 of 5 scratchesMax. Width: 454.9 μm, 587.5 μm, 622.2 μm, 577.9 μm A = cracks measuringlarger than 150 μm

As shown in for Examples 9-10 of Table 4B, scratch performance usinghigh Na (15%) DIOX to achieve high surface CS (FIG. 15 ) maintainedscratch performance with no lateral cracking at 5N. Both DIOX conditionshave a first step in high Na salt (e.g., >10%NaNO₃), with 1st stephaving sufficient %Li to control frangibility while achieving deep depthof compression, and 2nd step in high Na salt without Li, with short timeto build a high CS spike on the surface. Using this DIOX approach, it isfeasible to achieve CS between about 700-800 MPa while still having nolateral cracking in Li containing glass compositions with Na₂O/Li₂O moleratio of <0.63.

FIG. 15 is a graph of stress (MPa) versus position (micrometers) from asurface for Examples 1, 9-10, and B (comparative). Examples 9-10, whichutilized DIOX, resulted in stress profiles that have high surfacecompressive stress (CS) with good scratch performance as measured by nolateral cracking at 5N (Table 4B). The DIOX stress profiles of Examples9-10 also have higher knee stresses as compared to the SIOX stressprofiles of Example B (comparative), which had lateral cracking at 5N(6%Na with surface CS of 725MPa), and of Example 1, which had no lateralcracking at 5N (12%Na 2%Li, with surface CS of 603 MPa).

For Examples 9-10, both shown in FIG. 15 , average compressive stressesover the depth of 15 micrometers to 40 micrometers based on the averagearea under the curve in FIG. 15 were, respectively: 203 MPa and 174 MPa.Example 9 had a depth of layer (DOL_(spike)) of 4.4 micrometers and aCS_(knee) of 280 MPa. Example 10 had a depth of layer (DOL_(spike)) of5.2 micrometers and a CS_(knee) of 233 MPa.

Examples G-I (Comparative)—Glass Articles Based on Composition A—DIOX

Glass articles were formed based on substrates according to CompositionA, which were ion exchanged according to the bath conditions describedin Table 5A.

TABLE 5A Step 1 Step 1 Step 2 Step 2 t NaNO₃/KNO₃/LiNO₃ Step 1 timeNaNO₃/KNO₃/LiNO₃ Step 2 time Example (mm) (mol %) (° C.) (hours) (mol %)(° C.) (hours) G 0.8 15.0/85.0/0 450 4  5.0/95.0/0 450 2 Comparative H0.8  5.0/95.0/0 450 4 15.0/85.0/0 450 2 Comparative

Table 5B provides the scratch data.

TABLE 5B Depth of Example 5N 8N Compression (DOC) G Lateral crackingLateral cracking 179 micrometers Comparative present present (22.4% ofthickness) H Lateral cracking Lateral cracking — Comparative presentpresent

As shown in Table 5B, for Example G (comparative) using high Na (15%) ina 1st DIOX step followed by a second step of extended time (>30 minutes)in low Na salt (<10%NaNO₃), with no Li resulted in lateral cracking at5N for a glass with Na₂O/Li₂O mole ratio of <0.63. Likewise, for ExampleH (comparative) using low Na (5%) in a 1st DIOX step followed by asecond step of high Na salt (15%NaNO₃), with no Li also resulted inlateral cracking at 5N for a glass with Na₂O/Li₂O mole ratio of <0.63.

FIG. 16 is a graph of stress (MPa) versus position (micrometers) from asurface for Examples 1 and 10; and B and G (comparatives). Example G(comparative) and Example 10 were DIOX-treated and resulted in stressprofiles having high surface CS. Example G (comparative) had poorscratch performance, and Example 10 had good scratch performance asmeasured by no lateral cracking in 5N. Example G (comparative) stressprofile had a surface CS of 828 MPa, and Example 10 had a surface CS of726 MPa. In FIG. 16 , the stress profiles are compared to the SIOXstress profiles of Example B (comparative), which had lateral crackingat 5N (6%Na with surface CS of 725 MPa), and of Example 1, which had nolateral cracking at 5N (12%Na 2%Li, with surface CS of 603 MPa).

All compositional components, relationships, and ratios described inthis specification are provided in mol % unless otherwise stated. Allranges disclosed in this specification include any and all ranges andsubranges encompassed by the broadly disclosed ranges whether or notexplicitly stated before or after a range is disclosed.

It will be apparent to those skilled in the art that variousmodifications and variations can be made to the embodiments describedherein without departing from the spirit and scope of the claimedsubject matter. Thus it is intended that the specification cover themodifications and variations of the various embodiments described hereinprovided such modification and variations come within the scope of theappended claims and their equivalents.

What is claimed is:
 1. A method of manufacturing a glass-based article,comprising: exposing a glass-based substrate having opposing first andsecond surfaces defining a substrate thickness (t) and having a lithiumaluminosilicate composition to an ion exchange treatment comprising afirst molten salt bath having a concentration of a sodium salt in arange from 8 mol % to 100 mol % to form the glass-based article, whereinthe glass-based article comprises: sodium having a non-zero varyingconcentration extending from a surface of the glass-based article to adepth of the glass-based article; a compressive layer extending from thesurface to a spike depth of layer (DOL_(spike)) from 4 micrometers to 8micrometers; and a molar ratio of potassium oxide (K₂O) to sodium oxide(Na₂O) averaged over a distance from the surface to a depth of theglass-based article of 0.4 micrometers that is from 0 to 1.8; andwherein at least one of the following is satisfied: a base compositionof the glass-based substrate comprises a molar ratio of sodium oxide(Na₂O) to lithium oxide (Li₂O) of less than or equal to 0.63; and at acenter of the glass-based article, a molar ratio of sodium oxide (Na₂O)to lithium oxide (Li₂O) is less than or equal to 0.63.
 2. The method ofclaim 1, wherein the glass-based article comprises an averagecompressive stress (CS_(avg)) of greater than or equal to 115 MPa over adepth from 15 micrometers to 40 micrometers.
 3. The method of claim 1,wherein the glass-based article comprises a depth of compression (DOC)that is greater than or equal to 0.19t and/or greater than or equal to150 micrometers.
 4. The method of claim 1, wherein the molar ratio ofpotassium oxide (K₂O) to sodium oxide (Na2O) is about 0.4 to 1.8.
 5. Themethod of claim 1, conducted using a single ion exchange treatment,wherein the first molten salt bath comprises: from 8 mol % to 100 mol %of the sodium salt; from 0 mol % to 10 mol % of a lithium salt; and from0 mol % to 90 mol % of a potassium salt.
 6. The method of claim 5,wherein the first molten salt bath comprises from about 70 mol % toabout 89 mol % of the potassium salt.
 7. The method of claim 1, whereinthe exposing further comprises second molten salt bath that follows thefirst molten salt bath, wherein: the first molten salt bath comprises:from 8 mol % to 100 mol % of the sodium salt; from 0 mol % to 10 mol %of a lithium salt; and from 0 mol % to 90 mol % of a potassium salt; andthe second molten salt bath comprises: from 8 mol % to 100 mol % of asodium salt; from 0 mol % to 10 mol % of a lithium salt; and from 0 mol% to 90 mol % of a potassium salt.
 8. The method of claim 7, wherein thefirst molten salt bath comprises from 8 mol % to about 15 mol % of thesodium salt.
 9. The method of claim 7, wherein the first molten saltbath comprises about 80 mol % to 90 mol % of the potassium salt.
 10. Themethod of claim 7, wherein the first molten salt bath comprises about 4mol % or less of the lithium salt.
 11. The method of claim 1, whereinthe glass-based article comprises a Knoop scratch initiation thresholdof greater than or equal to 5 N.
 12. The method of claim 1, wherein theglass-based article comprises compressive stress at a knee (CS_(knee))of greater than or equal to 115 MPa, and the DOL_(spike) is greater thanor equal to 4.4 micrometers and less than 8 micrometers.
 13. The methodof claim 1, wherein the glass-based article has a maximum compressivestress (CS_(max)) of greater than or equal to 500 MPa.
 14. A method ofmanufacturing a glass-based article, comprising: exposing a glass-basedsubstrate having opposing first and second surfaces defining a substratethickness (t) and having a lithium aluminosilicate composition to an ionexchange treatment comprising a first molten salt bath having aconcentration of a sodium salt in a range from 8 mol % to 100 mol % toform the glass-based article, wherein the glass-based article comprises:sodium having a non-zero varying concentration extending from a surfaceof the glass-based article to a depth of the glass-based article; acompressive layer extending from the surface to a spike depth of layer(DOL_(spike)) from 4 micrometers to 8 micrometers; and a molar ratio ofpotassium oxide (K₂O) to sodium oxide (Na₂O) averaged over a distancefrom the surface to a depth of the glass-based article of 0.4micrometers that is from 0.4 to 1.8.
 15. The method of claim 14, whereinthe glass-based article comprises an average compressive stress(CS_(avg)) of greater than or equal to 115 MPa over a depth from 15micrometers to 40 micrometers.
 16. The method of claim 14, wherein theglass-based article comprises a depth of compression (DOC) that isgreater than or equal to 0.19t and/or greater than or equal to 150micrometers.
 17. The method of claim 14, conducted using a single ionexchange treatment, wherein the first molten salt bath comprises: from 8mol % to 100 mol % of the sodium salt; from 0 mol % to 10 mol % of alithium salt; and from 0 mol % to 90 mol % of a potassium salt.
 18. Themethod of claim 17, wherein the first molten salt bath comprises fromabout 70 mol % to about 89 mol % of the potassium salt.
 19. The methodof claim 14, wherein the exposing further comprises a second molten saltbath that follows the first molten salt bath, wherein: the first moltensalt bath comprises: from 8 mol % to 100 mol % of the sodium salt; from0 mol % to 10 mol % of a lithium salt; and from 0 mol % to 90 mol % of apotassium salt; and the second molten salt bath comprises: from 8 mol %to 100 mol % of a sodium salt; from 0 mol% to 10 mol % of a lithiumsalt; and from 0 mol % to 90 mol % of a potassium salt.
 20. The methodof claim 19, wherein the first molten salt bath comprises from 8 mol %to about 15 mol % of the sodium salt.
 21. The method of claim 19,wherein the first molten salt bath comprises about 80 mol % to 90 mol %of the potassium salt.
 22. The method of claim 19, wherein the firstmolten salt bath comprises about 4 mol % or less of the lithium salt.23. The method of claim 14, wherein the glass-based article comprises aKnoop scratch initiation threshold of greater than or equal to 5 N. 24.The method of claim 14, wherein the glass-based article comprisescompressive stress at a knee (CS_(knee)) of greater than or equal to 115MPa, and the DOL_(spike) is greater than or equal to 4.4 micrometers andless than 8 micrometers.
 25. The method of claim 14, wherein theglass-based article has a maximum compressive stress (CS_(max)) ofgreater than or equal to 500 MPa.